Group based complete and incremental computer file backup system, process and apparatus

ABSTRACT

The present invention is capable of determining the rights to a file based on providing a descriptor. The descriptor can be calculated using an algorithm, which may be cryptographic and/or non-cryptographic. The descriptor may further be based on the file contents, metadata of the file, other file data, or any combination thereof to uniquely identify the file in a shared file repository. Since the descriptor is generated based on file data it will be the same regardless of which user generates it. Accordingly, only one copy of the file needs to be maintained in the shared file repository, thereby reducing the amount of network bandwidth required to assure the file is backed up and further reducing the amount of storage required to backup the files. This results in a vastly more efficient method of backup in terms of processing time, network bandwidth, and storage requirements.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of U.S. patent applicationSer. No. 13/236,257, filed Sep. 19, 2011, which is a continuation ofU.S. patent application Ser. No. 11/744,741, filed May 4, 2007, now U.S.Pat. No. 8,051,043, which claims the benefit of U.S. Provisional PatentApplication Ser. No. 60/746,607, filed May 5, 2006, the entiredisclosures of which are hereby incorporated herein by reference.

FIELD OF INVENTION

The present invention relates generally to computer data rights and dataidentity. More specifically, the present invention is applicable toimproving data management as it applies to ffile systems, computer databackup, and computers in general.

BACKGROUND

Modern society relies heavily on computers and computer networks(computer systems) and subsequently the Internet, as it is essentially alarge computer system. Managing what person or entity has rights to aparticular file is extremely difficult, resource intensive and criticalto maintaining the privacy of data. Current implementations of rightsmanagement and file identification are so inefficient that largeconcessions and compromises have been made across the computing field.

Rights management, in accordance with the prior art, is typically doneon a per user basis. A user is generally authenticated and is grantedrights on an individual or group basis. It is common for filesassociated with each user to be compared bit for bit or through the useof some algorithm. Common comparison methods include a crc-32 signature,a file size check, and a more robust md5 method that is typicallyemployed for larger files. File comparison is typically done in a manualprocess on large downloads. A large file would be supplied with an md5checksum. The user downloads the file and runs an md5 utility on thedownloaded file and verifies that the checksums match. Traditionally,separate copies of files are maintained for each user.

One inefficiency introduced when comparisons are performed relates tothe process of computer backup. Most backup techniques rely on taking aninitial image or full backup of the entire contents of a computersystem. Using initial images or full backups may result in very largebackups being created during computer backup processes. There arevarious techniques for reducing the size of backups that exclude partsof the file system and/or do not copy data already backed up. Onetechnique for reducing the size of the backups is to only copy filesthat do not already exist. This technology utilizes crc-32 as a checksumalong with file name designators to determine if a file is already inthe repository. Employing the crc-32 technique does not reasonablyguarantee the uniqueness of the file as there are many possiblecombinations of data of the same size that will generate the same crc-32data. Moreover, using the crc-32 technique has an inherent file rightsproblem and file identity problem. If duplicate files are not backed up,the backup space is essentially a shared system. With this shared systemone must determine which files each backup client has rights to.

Another such inefficiency is in the process of configuration management.Configuration management is the process of managing the configuration ofa computer system. This process includes capturing and restoringconfiguration sets. Configuration sets may contain file structures andconfiguration information, as well as scripts to update configurationinformation or manipulate a file system. The inefficiency lies in theinability of the system to guarantee the uniqueness of files.Configuration sets are complete bundles of relevant data. Manyconfiguration sets will have multiple copies of the same files simplybecause of the complexity of managing files that are not assured to beunique.

The list of inefficiencies with computer storage, management, and databackup systems continues almost indefinitely. For example, a significantamount of inefficiency exists in the process of email storage and othermessage storage techniques as well as application data storage.

SUMMARY

Accordingly, it is an object of the present invention is to provide amore efficient method and system for managing files, file rights, andfile identity.

In accordance with at least one embodiment of the present invention amethod for determining a reasonably unique credential is provided. Themethod generally comprising:

receiving a first inventory of electronic data stored on a first remotestorage medium, wherein the first inventory comprises at least onedescriptor;

comparing the at least one descriptor of the first inventory to a listof descriptors associated with a second inventory of electronic datastored on a backup data storage medium, wherein the second inventory ofelectronic data comprises electronic data from a plurality of storagemediums different from the first remote storage medium;

determining that a first descriptor from the at least one descriptor ofthe first inventory substantially matches a second descriptor from thelist of descriptors associated with the second inventory; and

reporting to the first remote storage medium that electronic dataassociated with the first descriptor is already stored in the backupdata storage medium.

As used herein, “electronic data” may correspond to electronic files,portions of electronic files, chunks of data, data structures, metadata,or any other piece of electronic data.

A descriptor may be a combination of file metadata (e.g., file storagelocation and other bibliographic information pertaining to the file) andcryptographic signature or signatures. The use of a descriptor, in oneembodiment, allows a multitude of files to be stored without anysubstantially identical files being stored more than once. This can bemade possible without actually providing the file and without comparingthe files bit for bit. A database and/or other software application canmanage the descriptors in a system that provides higher-levelfunctionality. In one embodiment, a higher-level functionality is usedbecause many files are exact copies of other files and need not bestored if file management issues can be overcome. Reducing the amount ofredundantly stored files is important because of the cost andlimitations in memory, storage, and network resources.

Another aspect of the present invention is a method and system that iscapable of determining a reasonably unique descriptor. The determineddescriptor may be a combination of file metadata and cryptographicsignature or signatures. The descriptor, in one embodiment, enables apossessor of the descriptor to authenticate that the user associatedwith the processor and subsequently the processor has the right to thefile even if the processor only posses the descriptor and no longerpossess the file. In such embodiment, the processor is enabled todetermine that it has rights to a particular file because determiningthe descriptor for a file, without ever possessing the file, isextremely difficult even when relatively weak cryptographic routines areused to generate the descriptor.

A further aspect of the present invention provides for the use ofcryptographic routines or algorithms. The cryptographic algorithms aresubstantially more difficult to break if the entity trying to break theroutine (“attacker”) does not have access to both the secret and themessage. In accordance with at least some embodiments of the presentinvention, an attacker has access to neither. This makes theauthentication of files very secure, as the unauthorized entity wouldhave to guess the file metadata as well as the signature or signatures,a task that is extremely difficult if not completely impractical toaccomplish. In fact, when multiple signatures are used to identify afile, one method for generating valid descriptors would be to start withan actual file, in which case all that would be accomplished by theattacker is they would be given access to a file they already have.

The term “automatic” and variations thereof, as used herein, refers toany process or operation done without material human input when theprocess or operation is performed. However, a process or operation canbe automatic even if performance of the process or operation uses humaninput, whether material or immaterial, received before performance ofthe process or operation. Human input is deemed to be material if suchinput influences how the process or operation will be performed. Humaninput that consents to the performance of the process or operation isnot deemed to be “material”.

The terms “determine”, “calculate” and “compute,” and variationsthereof, as used herein, are used interchangeably and include any typeof methodology, process, mathematical operation or technique.

The term “module” as used herein refers to any known or later developedhardware, software, firmware, artificial intelligence, fuzzy logic, orcombination of hardware and software that is capable of performing thefunctionality associated with that element. Also, while the invention isdescribed in terms of exemplary embodiments, it should be appreciatedthat individual aspects of the invention can be separately claimed.

These and other advantages will be apparent from the disclosure of theinvention(s) contained herein. The above-described embodiments andconfigurations are neither complete nor exhaustive. As will beappreciated, other embodiments of the invention are possible utilizing,alone or in combination, one or more of the features set forth above ordescribed in detail below.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram depicting a communication system in accordancewith certain embodiments of the present invention;

FIG. 2 is a block diagram depicting a communication device in accordancewith certain embodiments of the present invention;

FIG. 3 is a logical representation of a data structure employed inaccordance with certain embodiments of the present invention;

FIG. 4 is an example of a descriptor utilized in accordance with certainembodiments of the present invention;

FIG. 5 is a group-based backup data structure employed in accordancewith certain embodiments of the present invention;

FIG. 6 is a flow chart depicting aspects of a backup routine inaccordance with certain embodiments of the present invention; and

FIG. 7 is a flow chart depicting aspects of a restore routine inaccordance with certain embodiments of the present invention.

DETAILED DESCRIPTION

The invention will be illustrated below in conjunction with an exemplarydata storage and backup system. Although well suited for use with, e.g.,a system using a server(s) and/or database(s), the invention is notlimited to use with any particular type of communication system orconfiguration of system elements. Those skilled in the art willrecognize that the disclosed techniques may be used in any communicationapplication in which it is desirable to provide a group-based filebackup system.

The exemplary systems and methods of this invention will also bedescribed in relation to communications software, modules, andassociated communication hardware. However, to avoid unnecessarilyobscuring the present invention, the following description omitswell-known structures, network components and devices that may be shownin block diagram form, are well known, or are otherwise summarized.

For purposes of explanation, numerous details are set forth in order toprovide a thorough understanding of the present invention. It should beappreciated, however, that the present invention may be practiced in avariety of ways beyond the specific details set forth herein.

Furthermore, while the exemplary embodiments illustrated herein show thevarious components of the system collocated, it is to be appreciatedthat the various components of the system can be located at distantportions of a distributed network, such as a communication networkand/or the Internet, or within a dedicated secure, unsecured and/orencrypted system. Thus, it should be appreciated that the components ofthe system can be combined into one or more devices, such as anenterprise server, any device with permanent storage capabilities, orcollocated on a particular node of a distributed network, such as ananalog and/or digital communication network. As will be appreciated fromthe following description, and for reasons of computational efficiency,the components of the system can be arranged at any location within adistributed network without affecting the operation of the system. Forexample, the various components can be located in a backup server, atone or more users' premises, or some combination thereof. Similarly, oneor more functional portions of the system could be distributed between aserver, gateway, and/or associated communication device.

Referring initially to FIG. 1, a communication system 100 will bedescribed in accordance with at least some embodiments of the presentinvention. The communication system 100 generally comprises acommunication network 104, one or more communication devices 108, anenterprise server 112, a backup server 116 including a backupapplication 124 and a restore application 120, and a data storage area128.

The communication network 104 may comprise any type of informationtransportation medium and may use any type of protocols to transportmessages between endpoints. The communication network 104 may includewired and/or wireless communication technologies. Examples of thecommunication network 104 include, without limitation, a standard PlainOld Telephone System (POTS), an Integrated Services Digital Network(ISDN), the Public Switched Telephone Network (PSTN), a Local AreaNetwork (LAN), a Wide Area Network (WAN), the Internet, and any othertype of packet-switched or circuit-switched network known in the art. Inaddition, it can be appreciated that the communication network 104 neednot be limited to any one network type, and instead may be comprised ofa number of different networks and/or network types.

The communication devices 108 may be packet-switched and/orcircuit-switched and can include, for example, phones, IP phones,Personal Digital Assistants or PDAs, Personal Computers or PCs, laptops,packet-based H.320 video phones and conferencing units, packet-basedvoice messaging and response units, packet-based traditional computertelephony adjuncts, conventional wired or wireless telephones, cellularphones, and the like.

The enterprise server 112 may comprise a dedicated processor thatfunctions to provide services to selected client devices (e.g.,communication devices 108). The enterprise server 112 generally enablescommunications between two or more communication devices 108 connectedwithin an enterprise and further provides a point of connection for theenterprise to the communication network 104. The enterprise server 112may comprise any type of processing medium operable to performinstructions stored on an electronic data storage area. The term“switch” or “server” as used herein should be understood to include a anenterprise server, a device with permanent storage capabilities, orother type of telecommunications system switch or server, as well asother types of processor-based communication control devices such asmedia servers (i.e., email servers, voicemail servers, web servers, andthe like), computers, adjuncts, etc.

The backup server 116 is adapted to provide file backup facilities. Thebackup server 116 is characterized by the ability to manage a filebackup system for a group of users, each of which may be associated withone or more communication devices 108. In accordance with certainembodiments of the present invention, the backup server 116 is providedwith a backup application 124 to enable users to backup files from theirrespective communication devices 108 to either the backup server 116 orto the data storage 128. The backup application 124 may be available toonly subscribing users or certain communication devices 108.Alternatively, non-subscribing users/communication devices 108 may bepermitted to utilize the backup application 124 to store one or moreversions of data from a communication device 108 onto a remote storage128 facility. Computer media, such as the media that resides on acommunication device 108, has a failure rate that requires copies of thedata to reside elsewhere for many usage scenarios. These remote backupcopies can be restored to a communication device 108 the event offailure of the original media. This process is called backup andrestore, which is supported by the backup application 124 and restoreapplication 120 respectively. The backup application 124 and restoreapplication 120 maintained on the backup server 116 provide a centralsupport for the management of a group-based backup system. The backupand restore process has two primary approaches. One is an image or blockbased back up of the media residing on a communication device 108. Theother is a file-based backup. Variations may exist that combine filebased and block based backup approaches. In accordance with someembodiments of the present invention, a full copy of the existing datastructure on a communication device 108 can be backed-up via the backupapplication 124 and subsequently incremental and/or full backups can beperformed. Incremental backups for each communication device 108 maycopy only the data that has changed on that communication device 108since the last full or incremental backup. Restoration varies fromindividual files to complete media restoration.

Backup systems in accordance with embodiments of the present inventiontypically group backups by volume sets, where a volume set consists ofan entire image and incremental backups. Thus, each volume set backupcontains an entire image and snapshots of changes. Traditionally, noneof this information is shared across multiple volume sets despite thefact that typically most of these files are identical. Identical filesrepresent a majority of the files on each communication device 108. Thebackup server 116 is characterized by the ability to act as a manager ofan indexed storage of electronic data and has the ability to respond tocommunication devices 108 informing them whether a particular piece ofelectronic data is already stored. The communication devices 108 caneach uniquely identify each file to the backup server 116 assuring onlyone copy is actually stored even though a number of communicationdevices 108 have backed up the same file. The backup application 124combines the backups of all communication devices 108 to dramaticallyreduce storage and network requirements.

A reason for volume sets is to provide the assurance that a file canonly be retrieved by someone having rights to the file. Traditionally,this is assured in the volume set backup by restricting access to thebackup repository and various access rights. In accordance withembodiments of the present invention, the restore application 120restricts access to files by requiring the restorer (i.e., the person orcommunication device 108 requesting the restore) to provide thefilename, size, and unique signature of the file. This information isonly known internally to the software and retrievable from a previouslygenerated inventory. Accordingly, the backup application 124 and restoreapplication 120 work cooperatively to maintain a group-based file backupsystem on the data storage 128 that maintains only one copy of uniquefiles and allows access to such files by a plurality of communicationdevices 108 if those communication devices 108 can provide the properinformation, usually in the form of a descriptor, to the backup server116. If that information is provided to the backup server 116, then therequesting communication device 108 is allowed to restore or otherwiseaccess the file from the data storage 128. As can be appreciated by oneskilled in the art, the enterprise server 112 may also utilize thebackup facilities provided by the backup server 116. More specifically,the enterprise server 112 may perform backups of its own data and/orcoordinate backups of various communication devices 108 connected to theenterprise server 112.

Applications provided by the backup server 116, in accordance with atleast one embodiment of the present invention, are essentiallyclient/server applications but each client can be a server as mentionedearlier. The backup server 116 may maintain the inventories of all thebackups and can thus provide the files to communication devices 108 thathave or should have a particular file. If the system supported theability to provide a list or partial list of communication devices; withthe particular file and the ability to provide partial file transfer theserver the system becomes a distributed file distribution application.

Essentially the backup server 116 provides the capability for acommunity or group of users to coordinate file storage and share accessto files that are common between two or more users within the communityor group. Accordingly, the backup server 116 can provide eachcommunication device 108 a remote location for file backup but does notnecessarily have to allocate memory for each of the files on eachcommunication device 108. Rather, the backup server 116 can store asingle copy of a file and will provide that file to each user in thecommunity or group that can prove they have access to the file based ona supplied descriptor (e.g., identifier of a unique file and credentialproving access permissions).

The data storage 128 may correspond to any type of known data storagemedium or combination of storage mediums. A data storage 128 may includeany media used for persistent storage such as a hard drive or drives,optical storage drives, non-volatile RAM, Storage Area Network, ornetwork attached storage.

It should be emphasized that the configuration of the servers 112, 116,user communication devices 108, and other elements as shown in FIG. 1 isfor purposes of illustration only and should not be construed aslimiting the invention to any particular arrangement of elements.

It should also be noted that the backup server 116 is not a necessary inaccordance with certain embodiments of the present invention. Rather,the data storage 128 may be implemented as a local repository (e.g.,local to a communication device 108 or enterprise server 112) andsignificant efficiencies can still be realized.

With reference now to FIG. 2, components of a communication device 108,such as a communications or computing device, are depicted in blockdiagram form in accordance with embodiments of the present invention.The components may include a processor 204 capable of executing programinstructions. Accordingly, the processor 204 may include anygeneral-purpose programmable processor, digital signal processor (DSP)or controller for executing application programming. Alternatively, theprocessor 204 may comprise a specially configured application specificintegrated circuit (ASIC). The processor 204 generally functions to runprogramming code implementing various functions performed by thecommunication device 108.

A communication device 108 may additionally include memory 208 for usein connection with the execution of programming by the processor 204 andfor the temporary or long-term storage of data or program instructions.The memory 208 may comprise solid-state memory resident, removable orremote in nature, such as DRAM and SDRAM. Where the processor 204comprises a controller, the memory 208 may be integral to the processor204. The memory 208 may be volatile and/or non-volatile memory.

In addition, the communication device 108 may include one or more userinputs 212 and one or more user outputs 216. Examples of user inputs 212include, without limitation, keyboards, keypads, touch screens, touchpads, and microphones. Examples of user outputs 216 include, but are notlimited to, speakers, display screens (including touch screen displays),and indicator lights. Furthermore, it can be appreciated by one of skillin the art that the user input 212 may be combined or operated inconjunction with a user output 216. An example of such an integrateduser input 212 and user output 216 is a touch screen display that canboth present visual information to a user and receive input selectionsfrom a user.

A communication device 108 may also include data storage 220 for thestorage of application programming and/or data. In addition, operatingsystem software 224 may be stored in the data storage 220. The datastorage 220 may comprise, for example, a magnetic storage device, asolid state storage device, an optical storage device, a logic circuit,or any combination of such devices. It should further be appreciatedthat the programs and data that may be maintained in the data storage220 can comprise software, firmware or hardware logic, depending on theparticular implementation of the data storage 220.

The data storage 220 may further include a backup application 228 and arestore application 240 that provides functionality similar to thebackup server 116 described in relation to FIG. 1. The backupapplication 228 resident on the communication device 108 may provide theability to backup various files and other electronic data from thecommunication device 108 to a remote storage location such as datastorage 128. To facilitate coordination of a group-based backup system,the backup application 228 may be provided with a scanning module 232and file analysis module 236. The scanning module 232 is provided toperform an initial scan of local files to make a quick determination asto whether file data has been changed, updated, added, etc. The backupapplication 228 may employ the scanning module 232 to scan a selectednumber of storage drives or other storage media to create a shadow copyof a drive. By scanning a particular drive or similar storage medium,the scanning module 232 is capable of creating a file inventory for theselected drive. The file inventory reflects the current state of thedrive and may include a description of the hierarchical structure of thedrive. The scanning module 232 may also be implemented as a file systemmonitor that continuously tracks changes for a continuous real-timebackup solution.

While the scanning module 232 is configured to cursorily scan a selectedmedia, the file analysis module 236 is configured to perform a morein-depth analysis of files that the scanning module 232 has identifiedas possibly changed, updated, added, and so on. The scanning module 232may be adapted to apply a descriptor algorithm to each file identifiedas possibly altered. The application of the descriptor algorithm createsa unique descriptor of each file. In accordance with certain embodimentsof the present invention, the analysis module 236 is capable ofgenerating a hash comprising a unique alpha-numeric string based on thefile data itself The descriptor algorithm uses, as an input, the filedata including raw data and possibly metadata to create the descriptorthat uniquely (i.e., substantially uniquely) identifies the file or aportion of the file. The results of the application of the descriptoralgorithm (e.g., the generated hash corresponding to each file orportion of a file) may also be added to the inventory to help describethe current state of the drive.

The backup application 228 may then transmit the updated inventory ofthe descriptors or just changes to the inventory of the descriptors tothe backup server 116, where the backup server 116 can compare theinventory to files already stored in the data storage 128 to determinewhat files will need to be transmitted from the communication device 108to the backup server 116 to complete a backup of such files.

The restore application 240 may be provided to facilitate the transferof files from a backup server 116 to the communication device 108. Moreparticularly, the restore application 240 may utilize a scanning module232 and a file analysis module 236 similar to those provided for thebackup application 228 to determine what files need to be transferredfrom the backup server 116 to the communication device 108 during arestore operation. Rather than using the descriptors of files todetermine if a file needs to be downloaded to the backup server 116, therestore application 240 utilizes the descriptors to request access tothe files already stored in data storage 128. The restore application240 may utilize the scanning module 232 to determine if any filescurrently stored in local memory (i.e., the memory of the communicationdevice 108) have changed since the point-in-time corresponding to therequested restore. The scanning module 232 may check metadata of filesand compare the create time and edit time of the file with thepoint-in-time corresponding to the requested restore. If the files weremarked as altered some time after the identified point-in-time, then therestore application 240 may employ the file analysis module 236 todetermine if the alterations affected any content of the file. The fileanalysis module 236 may apply a descriptor generating algorithm to eachof the identified files and compare that with a historical inventory ofdescriptors from the identified point-in-time. Any files or portion of afile having a different descriptor may then be identified by the restoreapplication 240 as requiring replacement during the restore operation.Otherwise, if the file or portion of a file has not changed, then therestore application 240 may determine that the file or portion of filedoes not need to be transmitted from the backup server to thecommunication device 108 during the restore operation.

Although the backup application 228 and restore application 240 aredepicted as having a dedicated scanning module 232 and file analysismodule 236, one skilled in the art will appreciate that a singlescanning module 232 and file analysis module 236 may be provided in thedata store 220 and shared by the backup application 228 and restoreapplication 240.

The data storage 220 may also contain application programming and dataused in connection with the performance of other functions of thecommunication device 108. For example, in connection with acommunication device 108 such as a telephone or IP telephone, the datastorage 220 may include communication application software. As anotherexample, a communication device 108 such as a Personal Digital Assistant(PDA) or a general-purpose computer may include a word processingapplication in the data storage 220. Also, a communication device 108such as a portable music/video storage and playback device may includeapplications related to the playback of various stored content.

A communication device 108 may also include one or more communicationnetwork interfaces 244. Examples of communication network interfaces 244include, but are not limited to, a network interface card, a modem, awired telephony port, a serial or parallel data port, radio frequencybroadcast transceiver, a USB port, or other wired or wirelesscommunication network interfaces.

With reference now to FIG. 3, a data structure 300 used to manage filesand data structures in a backup/restore operation will be described inaccordance with at least some embodiments of the present invention. Thedata structure 300 may comprise a file name (or data structure name)field 304, a file data field 308, a descriptor generating algorithmfiled 312 and a descriptor field 316. The data structure 300 may bemaintained, completely or in part, at a communication device 108, anenterprise server 112, the backup server 116, or in data storage 128.The file name field 304 may be used to store the electronic file name ordata structure identifier. The file name field 304 may store the nameprovided to the electronic file upon creation of the file along with anyother identification information such as location in memory and thelike.

The file data field 308 may be utilized to store or represent file data.Non-limiting examples of file data that may be represented in the filedata field 308 include actual file data, file metadata such asdescriptive metadata (e.g., metadata that describes a resource forpurposes such as discovery and identification including elements liketitle, abstract, author, and keywords), structural metadata (e.g.,metadata that indicates how compound objects are put together, forexample, how pages are ordered to form chapters), and administrativemetadata (e.g., metadata that provides information to help manage aresource, such as when and how it was created (creating and modificationtimestamps), file type and other technical information, and who canaccess it).

The descriptor generating algorithm field 312 may comprise data relatedto a descriptor generating algorithm that is used to generatedescriptors for various files. In accordance with at least someembodiments of the present invention, the descriptor generatingalgorithm is an algorithm applied uniformly to all files. Communicationdevices 108, enterprise servers 112, and backup servers 116 alike shouldapply the descriptor generating algorithm uniformly such that a commonfile has the same descriptor associated with it, regardless of whichendpoint generated the descriptor. This uniform representation ofelectronic files by descriptors allows the backup server 116 to knowwith a reasonable amount of certainty when a particular file is alreadystored in the data storage 128. The descriptor may also serve as acredential for the communication devices 108 that wish to access thesingle copy of a stored file. If the descriptor is generated properly ateach endpoint a uniform identification system is created that willafford efficient group-based backup storage of electronic data. Examplesof a descriptor generating algorithm that may be utilized include,without limitation, an MD5 hash, SHA256, ssh256, crc-32, and any otherhash generating algorithm known in the art. The descriptor generatingalgorithm may be either a cryptographic or non-cryptographic algorithmdepending upon the desired level of security. Additional data may beprovided in the descriptor generating algorithm filed 312 outlining thevarious inputs that may be included in the preparation of thedescriptor. For example, a descriptor may be generated based simply uponthe actual file data. Portions of metadata may also be included asinputs to the descriptor generating algorithm.

The generated descriptor may then be stored in the descriptor field 316.As noted above, each electronic file or portion of a file may have adescriptor associated therewith. The descriptor is generally used as thecommon short-hand representative of the electronic file throughout thegroup-based backup system. Accordingly, a communication device 108 andbackup server 116 can reference a common file by independentlygenerating a descriptor for the file using an agreed upon descriptorgenerating algorithm. As can be seen in FIG. 4, the descriptor for aparticular file may be a combination of a number of descriptors such asdescriptors 404 a-M where M is generally greater than or equal to one.Each descriptor 404 may be used to represent a different portion of datafor a common file and each descriptor may represent a predeterminedlength of data. For instance, if a file is one that is not updatedfrequently, as determined by its metadata, then the file may be dividedinto 10 MB chunks and each chunk may have a unique descriptor associatedtherewith. Alternatively, a file that is updated frequently may bedivided into 1 MB chunks to provide a more granular set of descriptors.

The chunk descriptors may then be combined, usually in an additivefashion, to create a combined descriptor 408 that represents the entirefile. The use of chunk descriptors is useful in situations where only aportion of a file has changed since it was last backed up. Duringanalysis by the file analysis module 236, the changed chunks may beidentified by their new descriptors. Those changed chunks may be theonly data that the backup server 116 needs to perform a complete backupof the entire file. More specifically, a communication device 108 mayonly need to transmit those portions of a file that have changed insteadof sending the entire file which will reduce the amount of time requiredto complete the backup operation.

Separate inventories of descriptors may be maintained on a communicationdevice 108, enterprise server 112, and/or backup server 116. Thisaffords the ability to maintain separate backup inventories andpermissions for various communication devices 108 to the common datastorage 128 and common files stored therein.

Referring now to FIG. 5, a group-based backup data structure will bedescribed in accordance with at least some embodiments of the presentinvention. The backup data structure is typically maintained on thebackup server 116 as a reference to the identity of files and when thosefiles were backed up on a per-user basis. More specifically, the backupserver 116 may be designed to maintain inventories 504 for each useraccount. A first inventory 504 a may correspond to user A, a secondinventory 504 b may correspond to user B, and a third inventory 504 cmay correspond to user C. The inventory 504 may be associated with asingle communication device 108 of a particular user. Alternatively, aninventory 504 may be maintained for a user that identifies files fromdifferent communication devices 108 associated with the same user. Thisway, when one communication device 108 fails, a user may utilize his/herentire inventory to restore files from all of his/her communicationdevices 108 back to the previously failed communication device 108.Included in a user's inventory may be a list of descriptors 508. Thelist of descriptors 508 for each user are a short-hand representation ofthe actual files, or portions of files, that have been recently backedup for the user's communication device 108.

The backup server 116 may additionally maintain list of backed up files512 currently stored in the common data storage 128. The backup server116 may reference the list of backed up files 512 through a descriptormapping. In other words, the file data itself may be maintained on thedata storage 128 and the backup server 116 may maintain its list ofbacked up files 512 as a list of descriptors. Accordingly, the backupserver 116 can quickly compare the descriptors associated with each userto the descriptors outlined in the list of backed up files 512 todetermined which files each user has access to. Accordingly, the backupserver 116 only has to maintain one copy of any file in the data storage128 and can utilize a descriptor mapping to determine which user and/orcommunication device 108 is allowed access to the one copy of a file.This is particularly useful in situations where a single file is storedon a number of different communication devices 108. Each communicationdevice 108 may utilize the file locally but desires a backup of the fileon the data storage 128. The backup server 116 can provide the backupfacilities for the file but does not have to maintain a separate copycorresponding to each copy in the communication system 100. Forinstance, user A has a file corresponding to descriptor 1 on his/hercommunication device 108. User B may also have the same filecorresponding to descriptor 1. The file corresponding to descriptor 1may be a commonly utilized word processing application, such asMicrosoft Word®, that has little to no differences between users. Thefile corresponding to descriptor 2, on the other hand, may be a fileunique to user A (e.g., macros or preferences for the word processingapplication) and are accordingly also backed up. User A will be the onlyuser able to access those preferences, unless another user has the exactsame preferences, because user A is the only one with the data thatresults in descriptor 2.

As a further example, the file corresponding to descriptor N maycomprise base application such as an operating system that is common toall users, or at least a large proportion of them. Rather thanmaintaining a separate copy of the same file multiple times, each userwith the file and the corresponding ability to generate descriptor Nwill be able to access the file from backup if such access is requiredduring a restore operation.

Although only three user accounts are depicted, one skilled in the artwill appreciate that the backup server 116 may support any number ofuser backup accounts. Advantageously, as the number of users utilizingthe backup accounts increases the overall efficiency of the systemincreases since the probability of having duplicate files on two or morecommunication devices 108 increases. Furthermore, efficient backups ofthe data and subsequent restores are facilitated automatically by theuse of descriptors. This obviates the need for a user to identify whichfiles he/she wants to send across the network 104 during backup in anattempt to increase backup efficiency. Rather, the backup server 116automatically identifies the duplicate files, or portions of files, andthen requests non-duplicate files or portions of files to be transmittedfrom the communication device 108 to the backup server 116 for storage.

With reference to FIG. 6, a backup routine will be described inaccordance with at least some embodiments of the present invention.Although the following description is mostly in relation to full filesand descriptors corresponding to full files, one skilled in the art willappreciate that similar methods may be applied to portions of files,data chunks, data structures, and corresponding descriptors. The routinebegins when a media or number of media are selected for backup at acommunication device 108 or enterprise server 112 (step 604). A typicalselection for a media might be a C: drive of a communication device 108or a network drive. The user may also select exclusions from the media,which are sets of files that are not to be backed up. The exclusions maybe definable based on common criteria. Examples of exclusions that maybe defined by a user include temporary or cache files residing on theselected media. Of course, the user is not required to select anyexclusions.

After selecting one or more media for backup, the method continues withthe scanning module 232 on the communication device 108 scanning theselected media (step 608). In this step the scanning module 232 maycreate a shadow copy of the drive that provides the ability to read acrash consistent version of the drive as it existed at the point theshadow copy was created. More specifically, the scanning module 232 maycreate a snapshot that, at a minimum, identifies the electronic data(e.g., files) resident on the selected media and the time at which thosefiles resided there. The metadata of the various files in the selectedmedia may be scanned to determine if any files have a changed timestampthat is more recent than the last backup.

Thereafter, the scanning module 232 may update the file inventory forthe selected media (step 612). The scanning module 232 may recursivelyexamine the selected media comparing it to what is in the lastinventory. If there was no previous backup for the selected media, thenall electronic data on the selected media are considered new to thebackup. Alternatively, if there was a previous backup, then the scanningmodule 232 may attempt to identify only the electronic data that haschanged or been added since the last backup. In step 616, the scanningmodule 232 determines if there is any data on the selected media thathave been changed or added. If any changes or additions were identified,then the scanning module 232 continues by identifying the changed or newelectronic data (step 620). The changed or new electronic data may beidentified by file name or by memory location. Electronic data that hasbeen deleted from the media may also be considered changed. As a part ofidentifying the changes, the scanning module 232 may update itsinventory of files based on file name.

Following the identification of changes to the various files and otherelectronic data on the media, the backup application 228 employs thefile analysis module 236 to apply the predetermined descriptorgenerating algorithm to each identified piece of data (step 624). Inother words, the file analysis module 236 applies the descriptorgenerating algorithm to any file, portion of file, chunk of data, ordata structure that has been identified as changed or new to create anew descriptor corresponding to that piece of data.

Once the descriptor generating algorithm has been properly applied toeach identified piece of data, the file analysis module 236 continues byupdating the descriptor inventory locally (step 628). The updateddescriptor inventory may include the new descriptors for the data thathas changed or been added as well as voids for files that have beendeleted or otherwise removed from the selected media. In addition toresults of the application of the descriptor generating algorithm,markers identifying sizes of chunks of files and correspondingdescriptors may be included in the updated descriptor inventory. Withthe descriptor inventory updated, the backup application 228 compressesthe descriptor inventory (step 632). Any known type of file compressionalgorithm may be employed in this step. The compression of thedescriptor inventory helps reduce the amount of bandwidth, andsubsequent upload time, required to transmit the descriptor inventoryacross the communication network 104.

The compressed descriptor inventory is then transmitted across thecommunication network 104 and uploaded to the backup server 116 (step636). Subsequently, the descriptor inventory is decompressed by thebackup server 116 and stored as a part of the user's inventory 504 inthe list of descriptors 508. In addition to updating the list ofdescriptors 508, the backup server 116 may also record the time at whichthe backup occurred for facilitation of future restore operations.

The backup server 116 may then utilize its backup application 124 tocompare the received descriptor inventory to descriptors in the list ofbacked up files 512 (step 644). In this comparison step, the backupapplication 124 then determines for each descriptor in the receiveddescriptor inventory, whether the corresponding file, file portion,chunk of data, or data structure is already stored in the data storage128. Based on the comparison step, the backup application 124 identifieselectronic data portions that are not yet stored in the data storage 128(step 648). The backup application 124 then generates a list of dataportions (e.g., a list of files) that need to be uploaded because theyare not currently on the data storage 128. The list of data portions,usually in the form of descriptors, is then sent back to thecommunication device 108 (step 652).

The communication device 108 receives the list of descriptors andidentifies the corresponding files, portions of files, chunks of data,or data structures that need to be uploaded to the backup server 116 tocomplete the backup operation (step 656). The communication device 108then employs the backup application 228 to compress the identifiedelectronic data (step 660). As previously noted, the compressionalgorithm utilized during this step may correspond to any compressionalgorithm known in the art. Furthermore, the compression may be skipped,but does help reduce the file transmission size.

The compressed electronic data, along with their correspondingdescriptors, are then uploaded to the backup server 116 (step 664). Thestep of comparing descriptors does require additional processing asopposed to simply uploading all of the files from the communicationdevice 108 to the backup server 116. However, by performing thispreliminary check of descriptors the amount of data transmitted may begreatly reduced if the backup server 116 has copies of most of thefiles. Since file data, especially for larger applications, can oftenhave a significant size, any reductions in the amount of data that isrequired for transmission can greatly increase the speed of a backupoperation.

Upon receiving the electronic data from the communication device 108,the backup server 116 may optionally decompress the data by employingthe reverse of the compression algorithm (step 668). Alternatively, theelectronic data may be maintained in its compressed format for storagesuch that required storage capacity is reduced. The backup server 116then stores the electronic data in the data storage 128 along with theircorresponding descriptor in the descriptors in the list of backed upfiles 512 (step 672). Thereafter, the backup server 116 stores theuser's descriptor inventory (i.e., all of the descriptors correspondingto all files on the communication device 108) along with the time ofbackup completion (step 676). Following storage of the user's descriptorinventory, the method ends (step 680).

Referring back to step 616, if the backup application 228 determinesthat there have been no changes to the selected media (e.g., either byaltering, adding, or deleting a file), then the method skips to step 676where the user descriptor inventory is maintained as the same and storedalong with the new backup time.

With reference now to FIG. 7, a restore/recover routine will bedescribed in accordance with at least some embodiments of the presentinvention. Although the following description is mostly in relation tofull files and descriptors corresponding to full files, one skilled inthe art will appreciate that similar methods may be applied to portionsof files, data chunks, data structures, and corresponding descriptors.The recover routine begins with the selection of a backup inventory forthe restore (step 704). In this step, a user essentially selects thepoint-in-time that they would like to have their communication device108 restored back to. This may be automatically selected if there isonly one backup for a particular communication device 108. Otherwise, ifthere are multiple backups, the user can select one of the backups thatcorrespond to the desired point-in-time. If the inventory or list ofinventories does not exist at the user's communication device, then itmay be retrieved from the backup server 116.

Thereafter, the user can select the target media(s) for the restore(step 708). A typical selection would be to restore a C: drive of acommunication device 108 or a particular network drive associated withthe enterprise server 112.

After the target media has been selected, the restore application 240 ofthe communication device 108 scans the selected target media andcompares the selected media with the inventory (step 712). In thescanning step, the restore application 240 may employ the scanningmodule 232 to check the metadata of the various files stored on themedia to determine if the files or other electronic data have an updatedtimestamp that is more recent that the selected point-in-time. If theupdated timestamp is older than the selected point-in-time, then theremay be no need to restore that particular file or electronic data sinceit already resides on the communication device 108 in the form that itdid during the backup step. However, if the scanning module 232determines that some changes, additions, or deletions of a file orelectronic data have occurred since the identified point-in-time, therestore application 240 compares the last media inventory to theselected media itself. Based on the comparison step, the restoreapplication 240 determines if there are any differences between themedia and the inventory (step 720). The changes that might occur to amedia since the last inventory took place may include changing, adding,or deleting files, portions of files, chunks of data, or data structuresfrom the media.

If any differences are detected, the method continues by identifying thechanged electronic data and its corresponding descriptor from theinventory (step 724). More specifically, after the scanning andcomparison step, electronic data that is identified as potentiallydifferent due to timestamp differences are analyzed to generate thedescriptors. If the descriptor is different from the previousdescriptor, then the former descriptor is added to the list of files torestore. This can eliminate the need to restore large amounts of data incertain scenarios. For instance, during a restore of a particular backupof a communication device 108 over another communication device 108 sucha feature may be useful. However, most electronic data does not usuallychange since its previous backup and such data would be identified asunchanged if not by the scanning step, then by the comparison of thedescriptors. The descriptors from the inventory represent the electronicdata at the time the last backup occurred. Those files or electronicdata that have changed since the identified point-in-time are thenmarked for restoration (step 728). More specifically, in accordance withcertain embodiments of the present invention, the descriptorscorresponding to the electronic data are marked for restoration.

Once the descriptors have been marked for restoration, the restoreapplication 240 continues by determining if any directories in theinventory are not present in the target media (step 732). If there areany directories in the inventory and not in the media, the restoreapplication 240 creates those directories in the target media (step736). The information required to create such directories may beprovided from the structure of the inventory. Depending upon theconfiguration of the present invention and data in the inventory,existing directories and files are left alone, if possible, renamed, ordeleted to reflect the structure defined by the inventory. Aftercreation of the requisite directories, or in the event such a creationwas not necessary, the restore application 240 requests that the backupserver retrieve the electronic data (step 740). In this step, therestore application 240 may first look in the most recent backups on thecommunication device 108 itself or some other local media. If the sameor reasonably similar descriptors exist indicating that an identicalfile exists locally on the local communication device 108, theelectronic data will be copied from the local copy instead of from thebackup server 116. This optimization is extremely effective in the casewhere a separate machine is being used to restore the backup to a drivethat will subsequently be installed into another machine. Thiseliminates having to download the operating system, for example,assuming the operating systems are the same or similar. If theelectronic data is not available locally, then the restore application240 provides the list of descriptors that have been marked for restoreback to the backup server 116. The backup server 116 utilizes thedescriptor to file mapping to retrieve the requested electronic datafrom the data storage 128. The backup server 116 is capable of allowingthe communication device 108 to access only those files and otherelectronic data listed in the inventory associated with thecommunication device 108. The files that the communication device 108never had, and therefore cannot generate the corresponding descriptor,will be maintained securely in the data storage 128. Accordingly, thedescriptor in this step acts as a credential to the files or electronicdata that were previously backed up from the communication device 108.

After the backup server 116 has retrieved the identified electronicdata, the backup server 116 downloads the electronic data to therequesting communication device 108 (step 748). The received data issubsequently received and decompressed by the communication device 108which then assembled on the target media (step 752). Then the restoreapplication 240 stores the all of the electronic data on the targetmedia (step 756). In this step, the file is moved, if possible, into itsoriginal location and all metadata is finalized including timestamps,attributes, Access Control Lists (ACLs), and so on. In addition toassembling the electronic data and storing it on the target media, therestore application 240 sets the metadata for the electronic data (step760). The directories in the inventory which were not on the targetmedia (i.e., were added to the target media in step 736) may also havetheir metadata restored by the restore application 240. Files anddirectories that currently exist on the target media and are not in theinventory may be optionally renamed, deleted, touched, or left alonedepending upon user preferences.

Following the reassembly and restoration of the target media the restoreapplication 240 determines if there are any files or other electronicdata not currently capable of a restore (step 764). Such a situationtypically arises if a file is currently open or in use by anotherapplication. If such a situation exists, the restore application 240will identify and set such files and electronic data for a restore uponreboot and the corresponding files and electronic data received from thebackup server 116 will be maintained in a temporary data storage areauntil the system reboots (step 768). After the files and electronic datanot currently capable of a restore have been set for restore uponreboot, or if there are no such files, the method ends (step 772).

As an additional embodiment of the present invention, an inventory ofthe protected media can be generated. This inventory is a list of allfiles with corresponding descriptors. The file descriptor may containfile information such as file length, ACLs or file rights, full path andfile name, file signature, create timestamp, modify timestamp, and lastaccessed timestamp. The file descriptor may actually consist of multiplefile descriptors using multiple cryptography type algorithms such as md5ssh256 and the file length. The descriptor will reasonably assure theuniqueness of the file. Thus no two different files of the same lengthand usable data could have the same signature with a reasonable amountof assurance as long as those files have some small difference. Theinventory is stored both locally and on the server.

In accordance with an alternative embodiment of the present invention,when a new inventory is generated, the generation can be a fullgeneration where the entire backup configuration is walked as in theinventory generation. This generation could be generated throughiterating through the list of all files and only generating newsignatures where the modify timestamp has changed. This generation couldbe generated through a log kept by the application of all file writes tothe protected media if the operating system provides such an API. Thisnew inventory can be compared to the last full inventory and allsubsequent incremental inventories. This will provide a subset of allprotected files that have changed. This inventory can then compared tothe master inventory on the backup server 116. If the signature (i.e.,descriptor) exists the file is not backed up. If the descriptor does notexist on server the file is compressed and backed up on the server.

Some modern Operating Systems provide an API for notifying anapplication of file system changes. If the operating system providessuch an API the communication device 108 can provide the capability ofperforming real time incremental backup. When the operating systemnotifies the communication device 108 that a protected file is beingwritten to and subsequently closes the file the client will analyze thefile and check the master inventory on the backup server 116 if thedescriptor exists the file is not backed up. If the descriptor does notexist on server the file is compressed and backed up on the server. Thena real time incremental log will be appended with the new analysis.

The user may select a file to restore from a previous inventory. Thesystem then checks to see if the file exists if the file does not existthe file is retrieved from the server by the client providing thedescriptor of the file. If the file exists the descriptor is checked. Ifthe descriptor does not match the file is retrieved from the server bythe providing the descriptor of the file. If the descriptor matches theversion the file is retrieved from the server by providing thedescriptor and restored. The files are then compared bit for bit and ifthey do not match both uploaded to an error tracking area for furtheranalysis.

Full or multiple file restoration walks through the selected inventoryor subset restoring each file as in the individual restoration.

Certain files may be particularly difficult to backup. These files aretypically special operating system files or database data files. Theoperating system files such as swap files, registries, and logs aredifficult to backup because they are usually large or have a high degreeof volatility or both. The database files are difficult to backup forthe same reason as operating system files and the volatility issuetypically spans multiple files. These issues are addressed by variousOperating System and Database API's. These API's can usually be scriptedat the OS level copying the consistent data to a protected directory.The actual files would then be excluded. Ideally these API's would beused to assure consistency. Alternatively the system will employ severaltechniques to get consistent images of individual files and groups offiles. In the event that the file is modified in the process of backingup the file or file set. One technique would be to locally copy the fileand double verify the descriptor. This technique ensures the file hasnot changed and is consistent. Another technique is to copy the file orgroups of files and logically separating each file into blocks eachblock will be verified with a descriptor. If the copy block does notmatch the source block the block is recopied and the descriptorverification begins starts over. Once all of the descriptors match thecopy is consistent. If a consistent copy can not be attained because offile volatility the backup of the file or file set is aborted. Thistechnique will work well for log files and low volatility databases.Another technique employs file system monitoring, which like theprevious technique is to copy the file or groups of files and logicallyseparating each file into blocks each block will be verified with adescriptor. Instead of recopying the block all writes will beintercepted and executed on the copied blocks until the point in timeimmediately after the copy completed. This will assure that the copy isconsistent.

The backup community, in accordance with at least one embodiment of thepresent invention, can flag files as belonging to a particularapplication. This would be at the snapshot level and the file level. Thename and other information such as security risk level. The communityusers could retroactively set these settings individually and a groupconsensus would be available as well as individual comments. This willenable the community to judge the validity of the files and quicklyascertain what a file is based on community feedback. Thus malware andspyware can be identified as well as the proper files to attain aparticular OS revision. Rolling back upgrades that were previouslyimpossible or unsupported by the vendor would be possible.

Since backup sets can be shared this system can become a P2Papplication. If individual signatures are shared and posted in asearchable form any file could be shared and accessible to anyone thatcan search.

While the above-described flowcharts have been discussed in relation toa particular sequence of events, it should be appreciated that changesto this sequence can occur without materially effecting the operation ofthe invention. Additionally, the exact sequence of events need not occuras set forth in the exemplary embodiments. The exemplary techniquesillustrated herein are not limited to the specifically illustratedembodiments but can also be utilized with the other exemplaryembodiments and each described feature is individually and separatelyclaimable.

Additionally, the systems, methods and protocols of this invention canbe implemented on a special purpose computer, a programmedmicroprocessor or microcontroller and peripheral integrated circuitelement(s), an ASIC or other integrated circuit, a digital signalprocessor, a hard-wired electronic or logic circuit such as discreteelement circuit, a programmable logic device such as PLD, PLA, FPGA,PAL, a communications device, such as a phone, any comparable means, orthe like. In general, any device capable of implementing a state machinethat is in turn capable of implementing the methodology illustratedherein can be used to implement the various communication methods,protocols and techniques according to this invention.

Furthermore, the disclosed methods may be readily implemented insoftware using object or object-oriented software developmentenvironments that provide portable source code that can be used on avariety of computer or workstation platforms. Alternatively, thedisclosed system may be implemented partially or fully in hardware usingstandard logic circuits or VLSI design. Whether software or hardware isused to implement the systems in accordance with this invention isdependent on the speed and/or efficiency requirements of the system, theparticular function, and the particular software or hardware systems ormicroprocessor or microcomputer systems being utilized. Thecommunication systems, methods and protocols illustrated herein can bereadily implemented in hardware and/or software using any known or laterdeveloped systems or structures, devices and/or software by those ofordinary skill in the applicable art from the functional descriptionprovided herein and with a general basic knowledge of the computer anddata storage arts.

What is claimed is:
 1. A method of synchronizing electronic data storedon a first client device with at least a second client device, themethod comprising: receiving, at a backup server, a first inventory ofelectronic data stored on a first remote storage medium associated witha first client device, wherein the electronic data comprises actual filedata to be backed-up from the first remote storage medium, wherein thefirst inventory comprises at least one descriptor and wherein the atleast one descriptor comprises a cryptographic signature computed basedon the actual file data, the cryptographic signature uniquelyidentifying the electronic data to be backed-up; comparing, at thebackup server, the at least one descriptor of the first inventory to alist of descriptors associated with a second inventory of electronicdata stored on a backup data storage medium, wherein the secondinventory of electronic data comprises shared electronic data from asecond remote storage medium associated with the at least a secondclient device as well a plurality of other storage mediums differentfrom the first and second remote storage mediums, and wherein the atleast one descriptor of the first inventory is compared with descriptorsin the second inventory that correspond, at least partially, to datastored on the backup data storage medium by storage mediums differentfrom the first remote storage medium; determining that a firstdescriptor from the at least one descriptor of the first inventory doesnot match a second descriptor from the list of descriptors associatedwith the second inventory; storing, on the backup data storage medium,the electronic data that is uniquely identified by the cryptographicsignature; determining that the second remote storage medium does nothave the electronic data that is uniquely identified by thecryptographic signature stored therein; determining that the secondremote storage medium is permitted to have the electronic data that isuniquely identified by the cryptographic signature; and providing theelectronic data that is uniquely identified by the cryptographicsignature from the backup server to the at least a second client deviceso that the electronic data that is uniquely identified by thecryptographic signature can be stored on the second remote storagemedium.
 2. The method of claim 1, wherein the step of determining thatthe second remote storage medium does not have the electronic data thatis uniquely identified by the cryptographic signature stored therein isinitiated in response to receiving a request from the at least a secondclient device.
 3. The method of claim 1, wherein the electronic datathat is uniquely identified by the cryptographic signature is providedfrom the backup server to the at least a second client device via adistributed communication network.
 4. The method of claim 3, wherein thedistributed communication network comprises the Internet.
 5. The methodof claim 3, wherein the electronic data that is uniquely identified bythe cryptographic signature is encrypted prior to being transmittedacross the distributed communication network.
 6. The method of claim 1,wherein the first client device and the at least a second client deviceare associated with a common user.
 7. The method of claim 6, wherein athird client device comprises a third remote storage medium that isincluded in the plurality of other storage mediums, wherein the thirdclient device is associated with a user that is different from thecommon user.